Combination of the words 'man' and 'bag' create 'mang' and 'wang' being slang for penis showing their attraction towards peni. This an insult towards anyone who is homosexual, as it refers to their unhealthy attraction towards women's things e.g. hand bags, flowers etc. Also this word can be used instead of gay, homosexual, faggot etc.
Guy1: Have you heard Elton John's new song.
Guy2: No-one listens to him, he's a mang o' wang.